The government's corporate average fuel economy (CAFE) requirement of 54.5 mpg by 2025 has pushed motor vehicle manufacturers to accelerate the use of lightweight materials in motor vehicles. As a result, it has been proposed to utilize low density sheet molding compounds in the construction of vehicle body panels, such as the hood, instead of standard density sheet molding compounds. More specifically, low density sheet molding compounds have a density of about 1.2 g/cm3 while standard density sheet molding compounds have a density of about 1.9 g/cm3. The key weight reduction in the formulation of low density sheet molding compounds versus standard density sheet molding compounds is replacing the CaCO3 component of the standard sheet molding compounds with low density glass bubbles.
One of the technical challenges faced in this effort is the low interfacial properties between glass bubbles and resin. More specifically, the smooth/hard surface of the glass bubbles causes weak bonding of the bubbles to the resin matrix which has a tendency to substantially decrease the overall mechanical performance of low density sheet molding compound.
This document relates to a new and improved surface treatment method for glass bubbles which functions to roughen the surface of the glass bubbles so as to allow for better adhesion to the resin.